i was wondering if some one could tell me the difference , advantages and disadvantages of using decal and materials.

Decals:
- Pro: Can be positioned very precisly.
- Pro: Can drive color, bump, specularity, reflection and all the other stuff.
- Pro: Is easier to create.
- Con: Is resolution-dependend.
- Con: Model has to be unwrapped and very well layouted to apply it distortionfree.

Material: (as long as we are talking about procedural, none-map-based materials)
- Pro: Can be applied by an easy drag and drop-operation to any amount of groups/models. Changes at the main-material will effect all the applied surfaces.
- Pro: Resolution-independend.
- Pro: Easy to apply without distortion.
- Con: Hard to create.
- Con: Can render longer if it is too complex.
- Con: Cant drive all the possible properties. For example as far as I know you cant use it for example for Cookie-Cuts, etc.

Material (map-based):
- Pro: Can be applied by an easy drag and drop-operation to any amount of groups/models. Changes at the main-material will effect all the applied surfaces.
- Con: Will distort too.
- Con: Not resolution-independend.

This is just a short overview... there are other circumstances when one or some of the statements here are not true, but in general it is like that.

Very nice overview Fuchur

some others:

materials:

pro - small file size
pro - properties can be animated
pro- can be saved in a PRJ


decals:

con - large file size
pro?con? - are animated as movies are, with multiple frames.
con - not saved in a PRJ

Sehr gut
danke
I really thank you all for the reply